Ctenucha rubroscapus, the red-shouldered ctenucha moth, is a moth of the family Erebidae. It was described by ÃÂdouard Ménétries in 1857. It is found in western North America, limited to low elevations west of the Cascade Mountains, south of Chehalis in Washington.
The length of the forewings is 19âÂÂ20 mm.
The larvae feed on Poaceae and Cyperaceae species, including species of the genera Dactylis and Elymus.